Ionic conjugated microporous polymer nanofiltration membrane with optimized site for rapid separation of dyes

Nowadays, organic dyes are one of the main sources of water pollution, posing a serious threat to human life and public safety, and the development of materials capable of eliminating dyes from water is challenging due to their high chemical stability that makes them difficult to eliminate. Herein, we report an example of a dense and continuous ionic conjugated microporous polymer (iCMP) membranes constructed by a surface-initiated polymerization strategy, in which the pore size of the iCMP membranes was tuned by exchanging different counter-anions (Cl-, Br-, BF4-) to achieve effective separation of organic dyes in water. Our study shows that the BF4- exchanged iCMP membrane has the smallest pore size, allowing it to effectively separate organic dyes in water without loss of water permeability (water permeability can reach as low as 447.9 L m−2 h−1 MPa−1 and rejection can reach as low as 99.5 % or more), which is far superior to commercially available membranes. This strategy of incorporating size regulation in two-dimensional membrane materials may evolve into a versatile platform for precision separations.